It is well known in copying machines to provide margining means for rendering the zones adjacent to the image image-free. Image transfer means are provided for transferring the image onto a receiving material and adjustment means are provided for adjusting the relative position of image and receiving material with respect to each other before transfer of the image.
For example, in U.S. Pat. No. 4,046,467 an electrophotographic copying device is described in which one of a number of fixed areas of an image carrier is brought into contact with a sheet of receiving material when a copy is being made. In this process an image of an original can be formed by projection at one position in that area which is adjustable.
The margining means are automatically adjusted so as to render image-free zones adjacent to the image regardless of the position of the image on the image carrier. A problem with automatic adjustment is that in the case of an adjustment in which the position of the image on the image carrier does not correspond with the position of the receiving sheet, a section of the image is not transferred onto the receiving material but remains present on the image carrier or is transferred onto the image transfer means. In both cases contamination of the copying device with image-forming material occurs.
Contamination of this kind is avoided in prior art copying machines (see, e.g., U.S. Pat. Nos. 4,129,378; 4,046,471 and 4,080,071) by not adjusting the margining means when adjusting the relative position of the image on the image carrier with respect to the receiving material. Rather, the margining means is permanently adjusted to the fixed areas where the receiving material makes contact with the image carrier. However, this method has the disadvantage that a zone next to the image formed on the image carrier may make contact with the receiving material and image-forming material deposited in the zone thus being transferred to the receiving material. Deposits of this kind are produced if the zone is insufficiently exposed, which happens if too little light reaches the image carrier from zones adjacent to an original that is in the exposure position, for example as a result of a shadow effect or through contamination of the plate which covers the original in the exposure position.
Various other means have been attempted including U.S. Pat. Nos. 4,272,180 and 4,501,490. The former patent describes a copier for forming images on opposite sides of the receiving material wherein the adjustment means adjusts the relative position of one of the images and receiving material. The latter patent describes a means for adjusting the relative positions by varying the magnification of the image forming step.
Accordingly, it is an object of the present invention to provide a copying means which overcomes the above mentioned disadvantages. It is a further object of the invention to provide in a copying device regulating means which adjusts the margining means so as to render image-free the zones adjacent to the image and also the zone of the image, which during the image transfer, falls outside the receiving material to prevent contamination with image-forming material and the occurrence of undesired deposition of image-forming material on the receiving material.